Constant Voltage and Constant Current DC to DC Converter

Linear Technology announces
the LT3956, an 80 V high-side current sense DC/DC converter designed to operate
as a constant-current and constant-voltage regulator. It is ideal for driving
high current LEDs as well as charging batteries and supercaps. Its 4.5 to 80 V
input voltage range makes it ideal for a wide variety of applications. The
LT3956 uses an internal N-channel MOSFET and can drive up to eighteen 350 mA
white LEDs from a nominal 12 V input, delivering in excess of 25 Watts. It incorporates a high-side current sense,
enabling use in boost, buck, buck-boost or SEPIC and flyback topologies. The
LT3956 delivers efficiencies of over 94% in boost mode, eliminating the need
for external heat sinking. A frequency adjust pin permits the user to program
the frequency between 100 kHz and 1 MHz, optimizing efficiency while minimizing
external component size and cost. Combined with a 5 x 6 mm QFN package, the
LT3956 offers a highly compact 25 Watt LED driver solution.

The LT3956 uses True Color
PWM dimming, delivering constant LED color with dimming ranges up to 3,000:1.
For less demanding dimming requirements, the CTRL pin provides a 10:1 analog
dimming range. The LT3956’s fixed frequency, current mode architecture ensures
stable operation over a wide range of supply and output voltages. A ground
referenced voltage FB pin serves as the input for several LED protection
features, enabling the converter to operate as a constant-voltage source.